**3.3. Toxic context**

The next challenge is to compare the tissue culture doses to the levels in the whales. Comparisons can be made to gain toxicological context; however, one must always bear in mind that cells grown on a dish are in a different environmental context than cells in a tissue and so the comparisons will not be precise. To contextualize the chromium toxicity data, we have converted our treatment concentrations to parts per million and converted the levels observed in the biopsies to molarity. This way we can determine if the levels we are using in the cell cultures are environmentally relevant concentrations.

Skin Biopsy Applications in Free Ranging Marine Mammals: A Case Study of Whale Skin Biopsies

*Right Whales (individual levels)*  **Whale ID Number Cr Tissue Level (ppm) Total Cr (uM)**  3646 4.9 94 2642 5.1 98 3301 6 115 1218 6.3 121 3351 8.1 156 1611 9 173 1607 10 192

Mean all right whales 7.1 135 *Sperm Whales (average by region)* 

**Location Cr Tissue Level (ppm) Total Cr (uM)** 

Sri Lanka 3.32 63 Canaries 3.69 70 Maldives 5.18 99 Mediterranean 5.21 100 Pacific Crossing 5.55 106 Papua New Guinea 5.72 109 Atlantic Ocean Crossing 6.28 120 Sea of Cortez 6.51 125 Indian Ocean Crossing 7.65 147

Chagos 7.95 152 Cocos 8.63 166 Australia 9.19 176 Mauritius 9.59 184 Galapagos 12.9 248 Seychelles 20.6 396 Kiribati 44.3 852 Bahamas 81.9 1575

Mean all sperm whales 9.3 179

Ocean pollution is emerging as a global priority. No longer can the world's oceans be considered an easy collective dumping site because even the most remote areas of the ocean are accumulating high levels of waste and pollutants. We now understand that any kind of pollution eventually ends up in the ocean. It may be carried by the wind, freshwater rivers

**Table 2.** Tissue Level Conversions

**4. Conclusions** 

as a Valuable and Essential Tool for Studying Marine Mammal Toxicology and Conservation 119

Our sodium chromate treatments convert to a range of 0.052-1.3 ppm and our lead chromate treatments convert to a range of 0.34-6.8 ppm (Table 1). Considering that average tissue levels for sperm whales and right whales were 9.3 and 7.0 ppm, respectively, our treatment concentrations are well below the average levels measured in whale skin (Tables 1 and 2). In fact, if we were to treat the cell cultures with the lowest sperm whale regional average measured in Sri Lankan waters (63.8 uM) we would kill all of the cells because our highest treatment concentration of 25 uM was highly cytotoxic (Figure 2) as measured by our cytotoxicity assay. Even our lowest detectable level in the sperm whale, 0.9 ug/g, is equivalent to treating cells with 6.38 uM and would induce cytotoxicity in approximately 65% of North Atlantic right whale cells and 90% of sperm whale cells. This level of treatment would also induce DNA damage in approximately 20% of both sperm whale and right whale metaphases. Given that our experimental doses are so much lower than the levels found in whales; this outcome raises concern about the impact of chromium pollution on whales regardless of the difference in environmental context between cells in a dish and cells in a tissue.


**Table 1.** Chromate Treatment Conversions.


**Table 2.** Tissue Level Conversions
